User terminal, radio base station, radio communication system, and radio communication method

ABSTRACT

In one aspect, a user terminal is provided that includes a transmitter that, if the user terminal is configured with a plurality of cell groups each including one or more cells, transmits uplink control information (UCI) including at least one ACK/NACK bit for each of the cell groups, and a processor that controls whether or not to bundle a plurality of ACK/NACK bits per cell group, independently depending on whether the UCI is transmitted by using a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). In another aspect, a radio base station is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application and, thereby,claims benefit under 35 U.S.C. § 120 to U.S. patent application Ser. No.15/524,700 filed on May 5, 2017, titled, “USER TERMINAL, RADIO BASESTATION, RADIO COMMUNICATION SYSTEM, AND RADIO COMMUNICATION METHOD,”which is a national stage application of PCT Application No.PCT/JP2015/078743, filed on Oct. 9, 2015, which claims priority toJapanese Patent Application 2014-226504 filed on Nov. 6, 2014. Thecontents of the priority applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a user terminal, a radio base station,a radio communication system, and a radio communication method for anext-generation mobile communication system.

BACKGROUND ART

For the universal mobile telecommunication system (UMTS) network, thelong term evolution (LTE) has been specified for further enhanced datarates and less delay (see Non-Patent Literature 1). The LTE advanced hasbeen specified for achieving even wider bands and higher speed thanthose of LTE, and the succeeding systems of LTE, such as future radioaccess (FRA), are under study.

The system band LTE Rel.10/11 includes at least one component carrier(CC) that uses an LTE system band as one unit. Band expansion throughthe aggregation of multiple component carriers is referred to as carrieraggregation (CA).

For LTE Rel.12, which is a more recent LTE system, various scenarios areunder study to use a plurality of cells in different frequency bands(carriers). When essentially identical radio base stations are used fora plurality of cells, aforementioned carrier aggregation can be used.When completely different radio base stations are used for a pluralityof cells, dual connectivity (DC) can be used.

LTE Rel.8 to Rel.12 have been specified assuming the exclusive use offrequency bands given to providers, i.e., licensed bands. For licensedbands, 800 MHz, 2 GHz, and 1.7 GHz, for example, are used.

LTE Rel.13 or later also target the use of frequency bands that do notrequire licenses, i.e., unlicensed bands. Unlicensed bands include 2.4GHz and 5 GHz, which are the same bands as Wi-Fi. LTE Rel.13 aims atcarrier aggregation of licensed bands and unlicensed bands(license-assisted access (LAA)) and will possibly aim at dualconnectivity and stand-alone unlicensed bands in future.

CITATION LIST Non Patent Literature

Non Patent Literature 1

3GPP TS 36.300 “Evolved Universal Terrestrial Radio Access (E-UTRA) andEvolved Universal Terrestrial Radio Access Network (E-UTRAN); Overalldescription; Stage 2”

SUMMARY OF INVENTION Technical Problem

Carrier aggregation according to LTE Rel.10/11/12 limits the maximumnumber of component carriers that can be allocated to each user terminalto five. LTE Rel.13 or later can allocate at least six componentcarriers to each user terminal in order to achieve more flexible andhigher-speed wireless communication and is studying use of extendedcarrier aggregation of these component carriers.

However, extension of PUCCHs and change of the MAC system would berequired to achieve extended carrier aggregation that can allocate atleast six component carriers to each user terminal.

An object of the present invention, which has been made to solve thisproblem, is to provide a user terminal, a radio base station, a radiocommunication system, and a radio communication method that enableproper operation of extended carrier aggregation that can allocate atleast six component carriers to each user terminal.

Solution to Problem

A user terminal of the present invention communicates with a radio basestation that configures a plurality of cell groups each of whichincluding one or more cells. The user terminal includes: a control unitthat controls six or more component carriers configured by the radiobase station; and a transmitting/receiving unit that receivesinformation on a plurality of component carriers configured by the radiobase station and feedbacks ACK/NACK information to one of the componentcarriers in each cell group.

Advantageous Effect of Invention

The present invention enables proper operation of extended carrieraggregation that can allocate at least six component carriers to eachuser terminal.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A, 1B, and 1C are diagrams for explaining conventional carrieraggregation.

FIG. 2 is a diagram for explaining extended carrier aggregation.

FIGS. 3A and 3B are diagrams for explaining an example of extendedcarrier aggregation according to the first embodiment.

FIG. 4 is a diagram for explaining an example of extended carrieraggregation according to the first embodiment.

FIGS. 5A and 5B are diagrams for explaining an example of extendedcarrier aggregation according to the first embodiment.

FIG. 6 is a diagram for explaining an example of extended carrieraggregation according to the second embodiment.

FIG. 7 is a diagram for explaining an example of extended carrieraggregation according to the second embodiment.

FIG. 8 is a diagram for explaining an example of extended carrieraggregation according to the second embodiment.

FIGS. 9A and 9B are diagrams for explaining an example of extendedcarrier aggregation according to the second embodiment.

FIGS. 10A and 10 B are diagrams for explaining MAC CE for controllingactivation/deactivation according to the third embodiment.

FIGS. 11A and 11B are diagrams for explaining activation/deactivation ofa cell group according to the third embodiment.

FIG. 12 is a diagram showing an example schematic configuration of aradio communication system according to this embodiment.

FIG. 13 is a diagram showing an example overall configuration of a radiobase station according to this embodiment.

FIG. 14 is a diagram showing an example functional configuration of aradio base station according to this embodiment.

FIG. 15 is a diagram showing an example overall configuration of a userterminal according to this embodiment.

FIG. 16 is a diagram showing an example functional configuration of auser terminal according to this embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will now be described withreference to the drawings.

LTE Rel.10 has employed carrier aggregation of up to five componentcarriers to widen the band, achieving a higher data rate (see FIG. 1A).

LTE Rel.11 has employed multiple timing advance (MTA) in which componentcarriers under inter-band carrier aggregation can be independentlycontrolled in different timings, achieving optimization of carrieraggregation of non-co-located component carriers (see FIG. 1B).

Carrier aggregation using multiple timing advance supports timingadvance groups (TAGs) classified according to their transmissiontimings. Referring to FIG. 1B, CC #1 to CC #3 are grouped into TAG #1,and CC #4 and CC #5 are grouped into TAG #2. Transmission timing controlbased on timing advance values is independently performed TAG by TAG.Accordingly, in carrier aggregation using multiple timing advances, auser terminal adjusts transmission timings for component carriers ineach multiple timing advance group, so that the times when the radiobase station receives uplink signals from the user terminal can besynchronized. For instance, it is possible to individually control thetimings of transmission of uplink signals from the user terminal throughCC #1 to CC #3 formed by the radio base station and through CC #4 and CC#5 formed by the remote radio head (RRH) connected to the radio basestation.

LTE Rel.12 has employed dual connectivity that aggregates cell groups(CGs) provided by a plurality of radio base stations connected throughnon-ideal backhaul which cannot neglect delays, achieving more flexiblearrangement (see FIG. 1C).

Dual connectivity assumes that scheduling is performed for theindividual schedulers of the plurality of radio base stations. Each userterminal is given a plurality of cell groups (CGs) by a radio basestation, and scheduling and HARQ control are performed separately forthe individual cell groups. This enables carrier aggregation ofcomponent carriers in cell groups formed by radio base stations, whichare placed in different positions and perform scheduling independently.Note that dual connectivity supports multiple timing advance in thegiven cell group.

Referring to FIG. 1C, CC #1 to CC #3 are grouped into Cell group #1, andCC #4 and CC #5 are grouped into Cell group #2. In Cell group #1, CC #1and CC #2 are grouped into TAG #1, and CC #3 is grouped into TAG #2. Incell group #3, CC #4 and CC #5 are grouped into TAG #3. Accordingly,with dual connectivity and carrier aggregation using multiple timingadvance, independent schedulers control signals transmitted through CC#1 to CC #3 formed by the first radio base station and the RRH connectedthereto and signals transmitted through CC #4 and CC #5 formed by thesecond radio base station, for example. Further, for each cell group,transmission timings for component carriers in different timing advancegroups are adjusted by coordination between the schedulers in the radiobase stations, so that the times when the radio base station receivesuplink signals from the user terminal can be synchronized.

However, as shown in FIGS. 1A to 1C, LTE Rel.12 or earlier limits themaximum number of component carriers that can be allocate (configured)to each user terminal to five.

In contrast, LTE Rel.13 aims at extended carrier aggregation (CAenhancement) without limiting the number of component carriers that canbe allocated to each user terminal. For example, as shown in FIG. 2,extended carrier aggregation aims at aggregation of 16 componentcarriers. Such extended carrier aggregation achieves more flexible andhigher-speed wireless communication. Thus, such extended carrieraggregation can aggregate a large number of component carriers ofcontinuous ultra-wide bands.

Such extended carrier aggregation has a problem in that it requires alarger size of overhead for feedback data required in an uplink controlchannel. Examples of control data fed back through uplink controlchannels include hybrid automatic repeat request-acknowledge (HARQ-ACK)and channel quality indicator (CQI). However, since conventional carrieraggregation assumes up to five component carriers, HARQ-ACK of only upto five component carriers can be multiplexed with a format of anexisting physical uplink control channel (PUCCH). Similarly, as for CQIfeedback, CQI of only a single component carrier can be transmittedthrough a PUCCH.

Besides, such extended carrier aggregation has another problem in thatit complicates user terminal control related to downlinks. In existingcarrier aggregation, physical downlink control channels (PDCCHs),physical downlink shared channels (PDSCHs), or physical uplink sharedchannels (PUSCHs) are independently processed for each componentcarrier. For this reason, as the number of component carriers increases,more channels (several times the number of component carries) need to becontrolled.

As described above, extended carrier aggregation requires PUCCHextension and change of the medium access control (MAC) system.

To solve this problem, the present inventors found a configuration forachieving extended carrier aggregation without requiring PUCCH extensionand change of the MAC control system and limiting the number ofcomponent carriers that can be allocated to each user terminal.

First Embodiment

In the first embodiment, extended carrier aggregation uses Dual-PUCCHsdefined by existing dual connectivity.

With dual connectivity, a PUCCH is allocated to one of the componentcarriers in each cell group. Thus, uplink control information (UCI)feedback is performed for each cell group separately. A componentcarrier given a PUCCH is a primary cell (PCell), for example.

Accordingly, a combination of dual connectivity and conventional carrieraggregation that can aggregate up to five component carriers achievesextended carrier aggregation that can support up to 10 componentcarriers (see FIG. 3A).

In FIG. 3A showing Cell group #1 including 5 CC of Component carriers #1to #5, and Cell group #2 including 5 CC of Component carriers #6 to #10,Component carriers #1 and #6 are each given a PUCCH. The user terminalperforms UCI feedback using the mechanism of existing LTE with up tofive component carriers in each cell group.

MTA, i.e., TA groups (TAGs) may be allocated to each cell group (seeFIG. 3B).

Increasing the number of component carriers to be given a PUCCH by onefrom five achieves extended carrier aggregation that can support up to15 or 20 component carriers, for example (see FIG. 4). To be specific, acombination of conventional carrier aggregation and dual connectivitycan increase the maximum number of component carriers that can besupported by extended carrier aggregation.

In the case shown in FIG. 4, extended carrier aggregation is performedfor Cell groups #1 to #4. Each cell group includes up to five componentcarriers. To be specific, this extended carrier aggregation supports 20component carriers. A PUCCH is allocated to one of the componentcarriers in each cell group. The user terminal performs UCI feedbackusing the mechanism of existing LTE with up to five component carriersin each cell group.

In the case shown in FIG. 4, dual connectivity may be applied to two ormore cell groups.

A user terminal may report band combinations that the user terminalsupports for downlink carrier aggregation and uplink carrieraggregation, to the network. The user terminal may report combinationsof bands that can be allocated to different cell groups, componentcarriers that can be given PUCCHs (capability), and the like to thenetwork.

The network transmits information on component carriers to undergodownlink carrier aggregation or uplink carrier aggregation, cell groupallocation, and a component carrier to be given a PUCCH in each cellgroup, to the user terminal by upper layer signaling.

The user terminal initiates communication by extended carrieraggregation based on the received information and feedbacks uplinkcontrol information (UCI) using the mechanism of existing LTE with up tofive component carries in each cell group.

According to LTE Rel.11, up to four TAGs can be set. However, withextended carrier aggregation, the maximum number of assignable TAGs maybe increased as the number of component carriers increases. For example,eight TAGs may be allocated as shown in FIG. 5A.

In general, a plurality of TAGs is allocated when radio base stationswith which the user terminal communicates use differenttransmission/reception points. For this reason, in actuality, a largenumber of (e.g., eight) TAGs are rarely required; thus, existingspecifications can probably support an adequate number of TAGs. Thenumber of TAGs may therefore be limited to below a certain level, unlikethe number of component carriers and cell groups. For example, as shownin FIG. 5B, a plurality of cell groups may be contained in the same TAG.In this case, the number of component carriers to undergo carrieraggregation can be increased without increasing the number of TAGs whosetiming should be separately controlled by the user terminal, therebyimproving the peak communication data rate while suppressing increasesin the cost of the user terminal and the consumption of battery.

Second Embodiment

In the second embodiment, extended carrier aggregation usesSingle-PUCCHs defined by existing carrier aggregation.

As described above, an existing PUCCH can only transmit HARQ-ACK of upto five component carriers. In use of extended carrier aggregation, tosolve the problem of an excess number of ACK/NACK (A/N) bits that can bemultiplexed into a single PUCCH, a plurality of component carriers maybe collected into one group in which A/N is bundled (bundling).

In the case shown in FIG. 6, 20 component carriers to undergo extendedcarrier aggregation are grouped into A/N groups #1 to #4. An A/N groupcorresponds to a TAG or cell group. This means that the user terminalmay regard a TAG or cell group as an A/N group. The component carriersin an A/N group receive a PDCCH or enhanced PDCCH (EPDCCH) containingdownlink assignment information (DL assignment) on the respectivecomponent carriers, and acknowledgement (ACK) ornegative-acknowledgement (NACK) indicating the results are bundled groupby group. The user terminal transmits UCI (A/N bundling) by using thePUCCH resource of a PCell. In the case shown in FIG. 6, the A/N bitcount is four. In use of multiple-input and multiple-output (MIMO) foreach component carrier, to transmit/receive double data, for example,the maximum A/N bit count is eight.

In this case, however, upon an error of reception of downlink assignmentinformation on any component carrier in an A/N group, although notproperly receiving downlink data assigned to the component carrier ofthe A/N group, the user terminal may determine that the result isacknowledgement (ACK) because it cannot even check the presence of data.To solve this problem, a radio base station may transmit downlinkassignment information not to individual component carriers but toindividual A/N groups (or TAGs or cell groups). To be specific, downlinkcontrol information (DL assignment) and uplink control information(HARQ-ACK) may be transmitted to individual A/N groups. Upon detectionof downlink assignment information, the user terminal bundles A/N of allassignments and if no downlink assignment information is detected, allassignments are discontinuous transmission (DTX).

In the case shown in FIG. 7, 20 component carriers to undergo extendedcarrier aggregation are grouped into A/N groups #1 to #4, and downlinkassignment and A/N bundling (bundling) are performed for each group.Downlink assignment information (DL assignment) is transmitted to one inan A/N group or a plurality of component carriers. The user terminal maydecode downlink assignment information on one or more component carriersby blind detection and component carriers through which transmission isperformed may be pre-specified by, for example, upper layer signaling.

A user terminal performs blind detection on multiple blocks of downlinkassignment information and determines which cyclic redundancy check(CRC)-checked blocks become downlink assignment information that isallocated to that user terminal. This downlink assignment informationincludes information on assignment to multiple component carriers. Thisinformation specifies component carriers assigned with data and includeslink adaptation information (e.g., frequency resource, the number ofMIMO ranks, modulation and coding scheme (MCS) level, and transportblock (TB) size) concerning each component carrier assigned with data.Link adaptation information may be common to, or different between, thecomponent carriers in the same group. As common information increases,overhead decreases. Greater numbers of different blocks of informationresult in more detailed link adaptation, leading to an improvement inthroughput.

It should be noted that as shown in FIG. 8, if there is only ACK/NACKfor the component carriers in one A/N group, a fallback to Rel.10/11carrier aggregation may be carried out. To be specific, when only thecomponent carriers in one A/N group detect downlink assignmentinformation, the user terminal may transmit A/N for the CCs in the A/Ngroup without bundling.

Alternatively, when the user terminal detects a PDCCH indicatingassignment information for one component carrier, a fallback toRel.10/11 carrier aggregation may be carried out. The user terminalperforms blind detection of both a PDCCH indicating assignmentinformation for one component carrier and a PDCCH containing assignmentinformation for a plurality of A/N-grouping-applied component carriers.In addition, upon detection of a PDCCH indicating assignment informationfor one component carrier, the user terminal may transmit A/N withoutbundling.

The PUCCH resource and PUCCH format may be changed between conventionalcarrier aggregation, which supports up to five component carriers, andextended carrier aggregation, which supports more than five componentcarriers. To be specific, different PUCCH resources and PUCCH formatsmay be used to transmit PUCCHs, depending on whether or not A/N bundlingis used.

As shown in FIG. 9A, when a PUSCH is assigned to a given targetcomponent carrier, the user terminal may transmit UCI (ACK/NACK) byusing a PUSCH resource without A/N bundling. This is because a PUSCH,which has large capacity that can contain a large number of bits, doesnot need compression by A/N bundling. In this case, the A/N bit count is20 to 40. As shown in FIG. 9B, when no component carrier is assignedwith a PUSCH, the user terminal may perform A/N bundling and transmitUCI (A/N bundling) using a PUCCH resource.

Third Embodiment

In the third embodiment, a method will be described of deactivatingunnecessary component carriers when there is no traffic during extendedcarrier aggregation.

With extended carrier aggregation, carrier aggregation of a large numberof component carriers achieves high peak rates but increases powerconsumption. It is therefore important to deactivate unnecessarycomponent carriers (de-activation) when there is no traffic. Withexisting LTE, however, a MAC control element (MAC CE) instructingactivation/deactivation has only seven bits (see FIG. 10A). To bespecific, activation/deactivation instructions are made with only sevencells.

To solve this problem, activation/deactivation instructions may be madefor individual groups of cells, such as TAGs, cell groups, or A/Ngroups. In this case, C_(i) in the MAC CE shown in FIG. 10A may beregarded as representing an activation/deactivation command for a cellgroup called SCell group index i. Notification of the SCell group indexis notified via an upper layer.

In a conventional scheme based on SCell index i, PCells and PSCellsunder dual connectivity are not deactivated. Accordingly, the MAC CEdoes not include C_(i) (=SCell index i) corresponding to a PCell.Therefore, if the conventional scheme based on SCell index i is replacedwith a scheme based on SCell group index i, an activation/deactivationcommand cannot be transmitted to the cell group including the PCell.Consequently, the cell group including the PCell is always active (seeFIG. 11A).

However, in order to suppress power consumption while there is notraffic, it is preferable that deactivation of SCells be possible evenin the cell group including the PCell. Accordingly, the third embodimentmay allow an activation/deactivation command to be transmitted to a cellgroup including a PCell or PSCell. Upon reception of an instruction todeactivate the cell group including a PCell or PSCell, the user terminalmay deactivate only the SCells in the cell group (see FIG. 11B). Asshown in FIG. 11B, the PCell or PSCell is always kept activeindependently of a command.

It should be noted that in addition to activation/deactivation ofindividual cell groups, group-by-group deactivation timer management maybe carried out. Upon selection of the cell group, the user terminalperforms total management, including deactivation timer control, on agroup basis, although it is traditionally carried out on a componentcarrier basis. This facilitates implementation of the user terminal.

In existing LTE, a MAC CE, which provides a power headroom report (PHR),reports activated/deactivated cells (see FIG. 10B). In particular, a MACCE, which provides a PHR, reports activated/deactivated cells and themaximum transmission power_(PCMAX,c) and PHR for each activated cell.For C₀, which does not exist in an existing PHR MAC CE, a new line maybe added to extend the MAC CE so that up to 16 activated/deactivatedcells can be reported, or the reserved bit (R) may be set to 0 or 1.

In the third embodiment, C_(i) reported by the PHR MAC CE may beregarded as a group index i. With C_(i) activated groups and maximumtransmission power P_(CMAX,c) and transmission power headroom PHR foractive component carriers may be reported. PHR timer and the like mayalso be managed on a group basis.

Alternatively, in addition to group-by-group activation/deactivation,group-by-group PHR may be used. The user terminal may report, throughC_(i), activated groups and maximum allowable power (e.g. P_(CMAX,g))and PHR for the individual activated groups. PHR for each group isdetermined by subtracting the total assignment power in the group fromP_(CMAX,g).

(Configuration of Radio Communication System)

The configuration of a radio communication system according to thisembodiment will now be described. This radio communication systememploys a radio communication method in which uplink transmissionoperation for LAA is performed in unlicensed bands.

FIG. 12 is a diagram showing an example schematic configuration of aradio communication system according to this embodiment. This radiocommunication system can employ one or both of dual connectivity andcarrier aggregation that unites a plurality of basic frequency blocks(component carriers) using a system band width for an LTE system as oneunit. Moreover, this radio communication system includes radio basestations that can use unlicensed bands.

As shown in FIG. 12, a radio communication system 1 includes a pluralityof radio base stations 10 (11 and 12) and a plurality of user terminals20 in cells formed by the radio base stations 10 and configured tocommunicate with the radio base stations 10. The radio base stations 10are connected to a higher station apparatus 30 and to a core network 40via the higher station apparatus 30.

Referring to FIG. 12, the radio base station 11 is a macro base stationwith relatively high coverage, forming a macro cell C1. The radio basestations 12 are small base stations with low coverage, forming smallcells C2. It should be noted that the number of the radio base stations11 and 12 is not limited that in FIG. 12.

For example, the macro cell C1 may be operated in a licensed band, andthe small cells C2 in an unlicensed band. Alternatively, part of thesmall cells C2 may be operated in an unlicensed band, and the rest ofthe small cells C2 in a licensed band. The radio base stations 11 and 12are connected to each other via an inter-base station interface (e.g.,optical fiber and X2 interface).

The user terminal 20 can be connected to both the radio base station 11and the radio base station 12. The user terminal 20 is assumed toconcurrently use the macro cell C1 and the small cell C2, which usedifferent frequencies, by carrier aggregation or dual connectivity. Forexample, the radio base station 11 using a licensed band can transmitthe user terminal 20 assistance information (e.g., downlink signalconfiguration) on the radio base station 12 which uses an unlicensedband. To achieve carrier aggregation between a licensed band and anunlicensed band, one radio base station (e.g., the radio base station11) may control the schedules of licensed band cells and unlicensed bandcells.

The user terminal 20 may be connected not to the radio base station 11but to the radio base station 12. For example, the radio base station 12using an unlicensed band may be connected to the user terminal 20 in astandalone manner. In this case, the radio base station 12 controls theschedules of unlicensed band cells.

Examples of the higher station apparatus 30 include, but should not belimited to, access gateway devices, wireless network controllers (RNCs),and mobility management entities (MMEs).

Examples of the downlink channels used in the radio communication system1 include physical downlink shared channels (PDSCHs) shared among userterminals 20, downlink control channels (physical downlink controlchannels (PDCCHs) and enhanced physical downlink control channels(EPDCCHs)), and physical broadcast channels (PBCHs). User data, upperlayer control information, and predetermined system information blocks(SIBs) are transmitted through PDSCHs. Downlink control information(DCI) is transmitted through PDCCHs or EPDCCHs.

Examples of the uplink channels used in the radio communication system 1include physical uplink shared channels (PUSCHs) shared among the userterminals 20 and physical uplink control channels (PUCCHs). User dataand upper layer control information are transmitted through PUSCHs.

FIG. 13 is a diagram showing an overall configuration of the radio basestation 10 according to this embodiment. As shown in FIG. 13, the radiobase station 10 includes a plurality of transmitting/receiving antennas101 for multiple-input and multiple-output (MIMO) transmission,amplifiers 102, transmitting/receiving units (transmitting units andreceiving units) 103, a baseband signal processing unit 104, a callprocessing unit 105, and an interface unit 106.

User data transmitted from the radio base station 10 to the userterminals 20 through the downlink channel is input from the higherstation apparatus 30 to the baseband signal processing unit 104 throughthe interface unit 106.

The baseband signal processing unit 104 performs packet data convergenceprotocol (PDCP) layer processing, user data division/combination,transmission processing for an RLC layer, such as transmissionprocessing for radio link control (RLC) retransmission control, mediumaccess control (MAC) retransmission control, such as transmissionprocessing, scheduling, transmission format selection, channel coding,inverse fast Fourier transform (IFFT) processing, and pre-coding forhybrid automatic repeat request (HARQ), and transfers the results toeach transmitting/receiving unit 103. Downlink control signals are alsosubjected to transmission processing, such as channel coding and inversefast Fourier transform, and the results are transferred to eachtransmitting/receiving unit 103.

Each transmitting/receiving unit 103 converts a downlink signal, whichis pre-coded for the corresponding antenna and output from the basebandsignal processing unit 104, to a wireless-frequency signal. Eachamplifier 102 amplifies the wireless-frequency signal generated byfrequency conversion and transmits it through the correspondingtransmitting/receiving antenna 101. Each transmitting/receiving unit 103is a transmitter/receiver, a transmitting/receiving circuit, or atransmitting/receiving device based on common understanding within thetechnical field of the present invention.

The transmitting/receiving unit 103 transmits information on six or morecomponent carriers configured to a user terminal 20 and receivesACK/NACK information fed back from one of the component carriers in eachcell group.

As for uplink signals, a wireless-frequency signal received at eachtransmitting/receiving antenna 101 is amplified by the correspondingamplifier 102, frequency-converted in the correspondingtransmitting/receiving unit 103 for conversion to a baseband signal, andthen input to the baseband signal processing unit 104.

In the baseband signal processing unit 104, user data in the receiveduplink signal is subjected to fast Fourier transform (FFT) processing,inverse discrete Fourier transform (IDFT) processing, error correctiondecoding, reception processing for MAC retransmission control, andreception processing for RLC layers and PDCP layers, and thentransferred to the higher station apparatus 30 through the interfaceunit 106. The call processing unit 105 performs call processing, such ascommunication channel allocation and release, management of the radiobase station 10, and management of the wireless resource.

The interface unit 106 transmits/receives signals (backhaul signaling)to/from the adjacent radio base station through an inter-BS interface(e.g., optical fiber and X2 interface). Alternatively, the interfaceunit 106 transmits/receives signals to/from the higher station apparatus30 through a predetermined interface.

FIG. 14 is a diagram showing a main functional configuration of thebaseband signal processing unit 104 included in the radio base station10 according to this embodiment. As shown in FIG. 14, the basebandsignal processing unit 104 included in the radio base station 10includes at least a control unit 301, a downlink control signalgenerating unit 302, a downlink data signal generating unit 303, amapping unit 304, a demapping unit 305, a channel estimating unit 306,an uplink control signal decoding unit 307, an uplink data signaldecoding unit 308, and a judgment unit 309.

The control unit 301 controls scheduling for downlink user datatransmitted through a PDSCH, downlink control information transmittedthrough one or both of a PDCCH and an extended PDCCH (EPDCCH), downlinkreference signals, and the like. Further, the control unit 301 controlsscheduling (assignment control) for RA preambles transmitted through aPRACH, unlink data transmitted through a PUSCH, uplink controlinformation transmitted through a PUCCH or PUSCH, and uplink referencesignals. Information on assignment control of uplink signals (uplinkcontrol signals and uplink user data) is transmitted to user terminals20 with the use of downlink control signals (DCI).

The control unit 301 controls assignment of wireless resources todownlink signals and uplink signals in accordance with instructions fromthe higher station apparatus 30 and feedback information from the userterminals 20. Thus, the control unit 301 serves as a scheduler. Thecontrol unit 301 is a controller, a control circuit, or a control devicebased on common understanding within the technical field of the presentinvention.

The downlink control signal generating unit 302 generates downlinkcontrol signals (one or both of PDCCH signals and EPDCCH signals) whichare assigned by the control unit 301. To be specific, the downlinkcontrol signal generating unit 302 generates, in accordance withinstructions from the control unit 301, downlink assignment thatprovides assignment information on downlink signals, and uplink grantsthat provide assignment information on uplink signals. The downlinkcontrol signal generating unit 302 is a signal generator or a signalgenerating circuit based on common understanding within the technicalfield of the present invention.

The downlink data signal generating unit 303 generates downlink datasignals (PDSCH signals) assigned to resources by the control unit 301.Data signals generated by the downlink data signal generating unit 303are coded and modulated according to coding rates and modulation methodsdetermined by CSI and the like sent from the user terminals 20.

The mapping unit 304 controls assignment of downlink control signalsgenerated in the downlink control signal generating unit 302 anddownlink data signals generated in the downlink data signal generatingunit 303 to wireless resources in accordance with instructions from thecontrol unit 301. The mapping unit 304 is a mapping circuit or a mapperbased on common understanding within the technical field of the presentinvention.

The demapping unit 305 performs demapping on uplink signals transmittedfrom the user terminals 20, thereby dividing the uplink signals. Thechannel estimating unit 306 estimates the channel state from referencesignals included in the received signals resulting from divisionperformed by the demapping unit 305, and feeds the estimated channelstate to the uplink control signal decoding unit 307 and the uplink datasignal decoding unit 308.

The uplink control signal decoding unit 307 decodes feedback signals(e.g., arrival confirmation signals) transmitted from the user terminalsthrough uplink control channels (PRACHs, PUCCHs), and feeds the resultsto the control unit 301. The uplink data signal decoding unit 308decodes uplink data signals transmitted from the user terminals throughphysical uplink shared channels (PUSCHs), and feeds the results to thejudgment unit 309. The judgment unit 309 performs retransmission controljudgement (A/N judgement) based on decoding results given by the uplinkdata signal decoding unit 308 and feeds the results to the control unit301.

FIG. 15 is a diagram showing an overall configuration of the userterminal 20 according to this embodiment. As shown in FIG. 15, the userterminal 20 includes a plurality of transmitting/receiving antennas 201for MIMO transmission, amplifiers 202, transmitting/receiving units(transmitting units and receiving units) 203, a baseband signalprocessing unit 204, and an application unit 205.

For downlink data, wireless-frequency signals received at a plurality oftransmitting/receiving antennas 201 are amplified by the respectiveamplifiers 202, frequency-converted in the respectivetransmitting/receiving units 203 for conversion to baseband signals.These baseband signals are subjected to FFT processing, error correctiondecoding, retransmission control reception processing, and the like inthe baseband signal processing unit 204. Downlink user data in thisdownlink data is transferred to the application unit 205. Theapplication unit 205 performs processing related to layers upper thanphysical layers and MAC layers. System information in the downlink datais also transferred to the application unit 205. Eachtransmitting/receiving unit 203 is a transmitter/receiver, atransmitting/receiving circuit, or a transmitting/receiving device basedon common understanding within the technical field of the presentinvention.

Meanwhile, uplink user data is input from the application unit 205 tothe baseband signal processing unit 204. The baseband signal processingunit 204 performs retransmission control (HARQ) transmission processing,channel coding, pre-coding, discrete Fourier transform (DFT) processing,inverse fast Fourier transform (IFFT) processing, and the like, and theresults are transferred to each transmitting/receiving unit 203. Eachtransmitting/receiving unit 203 converts a baseband signal, which isoutput from the base band signal processing unit 204, to awireless-frequency signal. Subsequently, each amplifier 202 amplifiesthe frequency-converted wireless-frequency signal which is thentransmitted through the corresponding transmitting/receiving antenna201.

The transmitting/receiving unit 203 receives information on a pluralityof component carriers configured by the radio base station 10 andfeedbacks ACK/NACK information to one of the component carriers in eachcell group.

FIG. 16 is a diagram showing a main functional configuration of thebaseband signal processing unit 204 included in the user terminal 20. Asshown in FIG. 16, the baseband signal processing unit 204 included inthe user terminal 20 includes at least a control unit 401, an uplinkcontrol signal generating unit 402, an uplink data signal generatingunit 403, a mapping unit 404, a demapping unit 405, a channel estimatingunit 406, a downlink control signal decoding unit 407, a downlink datasignal decoding unit 408, and a judgment unit 409.

The control unit 401 controls generation of uplink control signals(e.g., A/N signals) and uplink data signals on the basis of downlinkcontrol signals (PDCCH signals) transmitted from the radio base station10 and the retransmission control judgement results for the receivedPDSCH signals. Downlink control signals received from the radio basestation are output from the downlink control signal decoding unit 407,and the retransmission control judgement results are output from thejudgment unit 409. The control unit 401 is a controller, a controlcircuit, or a control device based on common understanding within thetechnical field of the present invention.

The control unit 401 can control six or more component carriersconfigured by the radio base station 10.

The uplink control signal generating unit 402 generates uplink controlsignals (feedback signals such as arrival confirmation signals andchannel state information (CSI)) in accordance with instructions fromthe control unit 401. The uplink data signal generating unit 403generates uplink data signals in accordance with instructions from thecontrol unit 401. It should be noted that the control unit 401 instructsthe uplink data signal generating unit 403 to generate an uplink datasignal when the downlink control signal received from the radio basestation includes an uplink grant. The uplink control signal generatingunit 402 is a signal generator or a signal generating circuit based oncommon understanding within the technical field of the presentinvention.

The mapping unit 404 controls assignment of uplink control signals(e.g., arrival confirmation signals) and uplink data signals to wirelessresources (PUCCH, PUSCH) in accordance with instructions from thecontrol unit 401.

The demapping unit 405 performs demapping on downlink signalstransmitted from the radio base station 10 and divides the downlinksignals. The channel estimating unit 406 estimates the channel statefrom reference signals contained in the received signals resulting fromdivision performed by the demapping unit 405, and feeds the estimatedchannel state to the downlink control signal decoding unit 407 and thedownlink data signal decoding unit 408.

The downlink control signal decoding unit 407 decodes downlink controlsignals (PDCCH signals) transmitted through physical downlink controlchannels (PDCCHs), and feeds scheduling information (information onassignment to uplink resources) to the control unit 401. It is alsooutput to the control unit 401 when any downlink control signal includesinformation on a cell to feedback an arrival confirmation signal orinformation on the necessity of RF adjustment.

The downlink data signal decoding unit 408 decodes downlink data signalstransmitted through physical downlink shared channels (PDSCHs) and feedsthe results to the judgment unit 409. The judgment unit 409 performsretransmission control judgement (A/N judgement) based on the decodingresults provided by the downlink data signal decoding unit 408, andfeeds the judgement to the control unit 401.

It should be noted that the present invention is not limited to theabove embodiments and various modifications can be made for itsimplementation. In the above embodiments, the sizes and shapes are notlimited to those shown in the attached drawings and can be modified invarious ways without departing from a range in which the advantageouseffects of the present invention can be obtained. Aside from that,various modifications can be made without departing from the scope ofthe present invention.

1. A user terminal comprising: a transmitter that, if the user terminalis configured with a plurality of cell groups each including one or morecells, transmits uplink control information (UCI) including at least oneACK/NACK bit for each of the cell groups; and a processor that controlswhether or not to bundle a plurality of ACK/NACK bits per cell group,independently depending on whether the UCI is transmitted by using aphysical uplink control channel (PUCCH) or a physical uplink sharedchannel (PUSCH).
 2. The user terminal according to claim 1, wherein thePUCCH is a PUCCH of a specific cell within a cell group corresponding tothe UCI, and the PUSCH is a PUSCH which is allocated to a given cellwithin the cell group belonging to the UCI.
 3. The user terminalaccording to claim 1, wherein when the UCI is transmitted by usingPUCCH, the processor bundles the plurality of ACK/NACK bits and when theUCI is transmitted by using the PUSCH, the processor cancels bundlingthe plurality of ACK/NACK bits.
 4. A radio base station comprising: areceiving that, if a user terminal is configured with a plurality ofcell groups each including one or more cells, receives uplink controlinformation (UCI) including at least one ACK/NACK bit for each of thecell groups; and a processor that controls transmission of a physicaldownlink shared channel (PDSCH) based on the ACK/NACK bit that iscontrolled to be bundled or not per cell group, independently dependingon whether the user terminal transmits the UCI by using a physicaluplink control channel (PUCCH) or a physical uplink shared channel(PUSCH).
 5. The user terminal according to claim 2, wherein when the UCIis transmitted by using PUCCH, the processor bundles the plurality ofACK/NACK bits and when the UCI is transmitted by using the PUSCH, theprocessor cancels bundling the plurality of ACK/NACK bits.